Hydroxyl PAMAM dendrimer-based gene vectors for transgene delivery to human retinal pigment epithelial cells

Ocular gene therapy holds promise for the treatment of numerous blinding disorders. Despite the significant progress in the field of viral and non-viral gene delivery to the eye, significant obstacles remain in the way of achieving high-level transgene expression without adverse effects. The retinal pigment epithelium (RPE) is involved in the pathogenesis of retinal diseases and is a key target for a number of gene-based therapeutics. In this study, we addressed the inherent drawbacks of non-viral gene vectors and combined different approaches to design an efficient and safe dendrimer-based gene-delivery platform for delivery to human RPE cells. We used hydroxyl-terminated polyamidoamine (PAMAM) dendrimers functionalized with various amounts of amine groups to achieve effective plasmid compaction. We further used triamcinolone acetonide (TA) as a nuclear localization enhancer for the dendrimer-gene complex and achieved significant improvement in cell uptake and transfection of hard-to-transfect human RPE cells. To improve colloidal stability, we further shielded the gene vector surface through incorporation of PEGylated dendrimer along with dendrimer-TA for DNA complexation. The resultant complexes showed improved stability while minimally affecting transgene delivery, thus improving the translational relevance of this platform.

Next-generation sequencing reveals low-dose effects of cationic dendrimers in primary human bronchial epithelial cells

Gene expression profiling has developed rapidly in recent years with the advent of deep sequencing technologies such as RNA sequencing (RNA Seq) and could be harnessed to predict and define mechanisms of toxicity of chemicals and nanomaterials. However, the full potential of these technologies in (nano)toxicology is yet to be realized. Here, we show that systems biology approaches can uncover mechanisms underlying cellular responses to nanomaterials. Using RNA Seq and computational approaches, we found that cationic poly(amidoamine) dendrimers (PAMAM-NH2) are capable of triggering down-regulation of cell-cycle-related genes in primary human bronchial epithelial cells at doses that do not elicit acute cytotoxicity, as demonstrated using conventional cell viability assays, while gene transcription was not affected by neutral PAMAM-OH dendrimers. The PAMAMs were internalized in an active manner by lung cells and localized mainly in lysosomes; amine-terminated dendrimers were internalized more efficiently when compared to the hydroxyl-terminated dendrimers. Upstream regulator analysis implicated NF-κB as a putative transcriptional regulator, and subsequent cell-based assays confirmed that PAMAM-NH2 caused NF-κB-dependent cell cycle arrest. However, PAMAM-NH2 did not affect cell cycle progression in the human A549 adenocarcinoma cell line. These results demonstrate the feasibility of applying systems biology approaches to predict cellular responses to nanomaterials and highlight the importance of using relevant (primary) cell models.

Modeling the effect of nano-sized polymer particles on the properties of lipid membranes

The interaction between polymers and biological membranes has recently gained significant interest in several research areas. On the biomedical side, dendrimers, linear polyelectrolytes, and neutral copolymers find application as drug and gene delivery agents, as biocidal agents, and as platforms for biological sensors. On the environmental side, plastic debris is often disposed of in the oceans and gets degraded into small particles; therefore concern is raising about the interaction of small plastic particles with living organisms. From both perspectives, it is crucial to understand the processes driving the interaction between polymers and cell membranes. In recent times progress in computer technology and simulation methods has allowed computational predictions on the molecular mechanism of interaction between polymeric materials and lipid membranes. Here we review the computational studies on the interaction between lipid membranes and different classes of polymers: dendrimers, linear charged polymers, polyethylene glycol (PEG) and its derivatives, polystyrene, and some generic models of polymer chains. We conclude by discussing some of the technical challenges in this area and future developments.

The role of caveolin-1 and syndecan-4 in the internalization of PEGylated PAMAM dendrimer polyplexes into myoblast and hepatic cells

To improve gene delivery efficiency of PEGylated poly(amidoamine) dendrimers in livers and muscles, the roles of syndecan-4 receptor and caveolin-1 protein in the endocytosis of PEGylated generation 5 (G5-PEG) or 7 (G7-PEG) dendrimers and plasmid DNA polyplexes were explored in C2C12 and HepG2 cells. Expression levels of syndecan-4 for both cell lines were downregulated by transfection of the cells with syndecan-4 specific siRNA. Caveolin-1 was upregulated by infecting the cells with adenovirus vector expressed caveolin-1 (Ad-CAV-1). The impact of syndecan-4 and caveolin-1 on endocytosis of G5-PEG/DNA or G7-PEG/DNA polyplexes was then measured by flow cytometry. Our results demonstrate that downregulation of syndecan-4 and upregulation of caveolin-1 significantly improved internalization of PEG-PAMAM dendrimer polyplexes in HepG2 cells; however, in C2C12 cells, downregulation of syndecan-4 decreased the internalization of the polyplexes while upregulation of caveolin-1 had no effect on internalization. Gene expression results for G5-PEG/pGFP on the two cell lines exhibited the same trends for syndecan-4 and caveolin-1 as was observed for endocytosis of the polyplexes. This study gives a clue how to take strategies by up- or down-regulation of the expressions of syndecan-4 and caveolin-1 to improve in vivo gene delivery efficiency of the PEG-PAMAM dendrimers in clinical transgenic therapy.

Comparative toxicological assessment of PAMAM and thiophosphoryl dendrimers using embryonic zebrafish

Dendrimers are well-defined, polymeric nanomaterials currently being investigated for biomedical applications such as medical imaging, gene therapy, and tissue targeted therapy. Initially, higher generation (size) dendrimers were of interest because of their drug carrying capacity. However, increased generation was associated with increased toxicity. The majority of studies exploring dendrimer toxicity have focused on a small range of materials using cell culture methods, with few studies investigating the toxicity across a wide range of materials in vivo. The objective of the present study was to investigate the role of surface charge and generation in dendrimer toxicity using embryonic zebrafish (Danio rerio) as a model vertebrate. Due to the generational and charge effects observed at the cellular level, higher generation cationic dendrimers were hypothesized to be more toxic than lower generation anionic or neutral dendrimers with the same core composition. Polyamidoamine (PAMAM) dendrimers elicited significant morbidity and mortality as generation was decreased. No significant adverse effects were observed from the suite of thiophosphoryl dendrimers studied. Exposure to ≥50 ppm cationic PAMAM dendrimers G3-amine, G4-amine, G5-amine, and G6-amine caused 100% mortality by 24 hours post-fertilization. Cationic PAMAM G6-amine at 250 ppm was found to be statistically more toxic than both neutral PAMAM G6-amidoethanol and anionic PAMAM G6-succinamic acid at the same concentration. The toxicity observed within the suite of varying dendrimers provides evidence that surface charge may be the best indicator of dendrimer toxicity. Dendrimer class and generation are other potential contributors to the toxicity of dendrimers. Further studies are required to better understand the relative role each plays in driving the toxicity of dendrimers. To the best of our knowledge, this is the first in vivo study to address such a broad range of dendrimers.

Targeting of follicle stimulating hormone peptide-conjugated dendrimers to ovarian cancer cells

Ovarian cancer is the most lethal gynecological malignancy. Current treatment modalities include a combination of surgery and chemotherapy, which often lead to loss of fertility in premenopausal women and a myriad of systemic side effects. To address these issues, we have designed poly(amidoamine) (PAMAM) dendrimers to selectively target the follicle stimulating hormone receptor (FSHR), which is overexpressed by tumorigenic ovarian cancer cells but not by immature primordial follicles and other non-tumorigenic cells. Fluorescein-labeled generation 5 (G5) PAMAM dendrimers were conjugated with the binding peptide domain of FSH (FSH33) that has a high affinity to FSHR. The targeted dendrimers exhibited high receptor selectivity to FSHR-expressing OVCAR-3 cells, resulting in significant uptake and downregulation of an anti-apoptotic protein survivin, while showing minimal interactions with SKOV-3 cells that do not express FSHR. The selectivity of the FSH33-targeted dendrimers was further validated in 3D organ cultures of normal mouse ovaries. Immunostaining of the conjugates revealed their selective binding and uptake by ovarian surface epithelium (OSE) cells that express FSHR, while sparing the immature primordial follicles. In addition, an in vivo study monitoring tissue accumulation following a single intraperitoneal (i.p.) injection of the conjugates showed significantly higher accumulation of FSH33-targeted dendrimers in the ovary and oviduct compared to the non-targeted conjugates. These proof-of-concept findings highlight the potential of these FSH33-targeted dendrimers to serve as a delivery platform for anti-ovarian cancer drugs, while reducing their systemic side effects by preventing nonspecific uptake by the primordial follicles.

Toxicity of PAMAM-coated gold nanoparticles in different unicellular models

Polyamidoamine (PAMAM) dendrimers are used for many pharmaceutical and biomedical applications. However, the toxicological risks of several PAMAM-based compounds are still not fully evaluated, despite evidences of PAMAM deleterious effects on biological membranes, leading to toxicity. In this report, we investigated the toxicity of generation 0 PAMAM-coated gold nanoparticles (AuG0 NPs) in four different models to determine how different cellular systems are affected by PAMAM-coated NPs. Toxicity was evaluated in two mammalian cell lines, Neuro 2A and Vero, in the green alga Chlamydomonas reinhardtii and the bacteria Vibrio fischeri. AuG0 NP treatments reduced cell metabolic activity in algal and bacterial cells, measured by esterase enzymatic activity (C. reinhardtii) and luminescence emission (V. fischeri). EC50 value after 30 min of treatment was similar in both organisms, with 0.114 and 0.167 mg mL(-1) for C. reinhardtii and V. fischeri, respectively. On the other hand, AuG0 NPs induced no change of mitochondrial activity in mammalian cells after 24 h of treatment to up to 0.4 mg mL(-1) AuG0 NPs. Change in the absorption spectra of AuG0 NP in the mammalian cell culture media may indicate an alteration of NP properties that contributed to the low toxicity of AuG0 NPs in mammalian cells. For a safe development of PAMAM-based nanomaterials, the difference of sensitivity between mammalian and microbial cells, as well as the modulation of NPs toxicity by medium properties, should be taken into account when designing PAMAM NPs for applications that may lead to their introduction in the environment.

Fate and transformation products of amine-terminated PAMAM dendrimers under ozonation and irradiation

This article deals with the degradation of a third-generation (G3) poly(amidoamine) (PAMAM) dendrimer under ozonation and irradiation. The identification and quantification of G3 PAMAM dendrimer and its transformation products has been performed by liquid chromatography-electrospray ionization-hybrid quadrupole time-of-flight-mass spectrometry. The dendrimer was completely depleted by ozone in less than 1 min. The effect of ultraviolet irradiation was attributed to hydroxyl-mediated oxidation. The transformation products were attributed to the oxidation of amines, which resulted in highly oxidized structures with abundance of carboxylic acids, which started from the formation of amine oxide and the scission of the CN bond of the amide group. We studied the toxicity of treated mixtures for six different organisms: the acute toxicity for the bacterium Vibrio fischeri and the microcrustacean Daphnia magna, the multigenerational growth inhibition of the alga Pseudokirchneriella subcapitata, and the seed germination phytotoxicity of Licopersicon esculentum, Lactuca sativa and Lolium perenne. Ozonation and irradiation originated transformation products are more toxic than the parent dendrimer. The toxicity of the dendrimer for the green alga was linked to a strong increase of intracellular reactive oxygen species with intense lipid peroxidation.

Intracellular environment-responsive stabilization of polymer vesicles formed from head-tail type polycations composed of a polyamidoamine dendron and poly(L-lysine)

For the development of effective drug carriers, nanocapsules that respond to micro-environmental changes including a decrease in pH and a reductive environment were prepared by the stabilization of polymer vesicles formed from head-tail type polycations, composed of a polyamidoamine dendron head and a poly(l-lysine) tail (PAMAM dendron-PLL), through the introduction of disulfide bonds between the PLL tails. Disulfide bonds were successfully introduced through the reaction of Lys residues in the PAMAM dendron-PLL polymer vesicles with 2-iminothiolane. The stabilization of PAMAM dendron-PLL polymer vesicles was confirmed by dynamic light scattering measurements. In acid-base titration experiments, nanocapsules cross-linked by disulfide bonds had a buffering effect during the cellular uptake process. The PAMAM dendron-PLL nanocapsules were used to incorporate the fluorescent dyes rhodamine 6G and fluorescein as a drug model. Cationic rhodamine 6G was generally not released from the nanocapsules because of the electrostatic barrier of the PLL membrane. However, the nanocapsules were destabilized at high glutathione concentrations corresponding to intracellular concentrations. Rhodamine 6G was immediately released from the nanocapsules because of destabilization upon the cleavage of disulfide bonds. This release of rhodamine 6G from the nanocapsules was also observed in HeLa cells by laser confocal microscopy.

Promising low-toxicity of viologen-phosphorus dendrimers against embryonic mouse hippocampal cells

A new class of viologen-phosphorus dendrimers (VPDs) has been recently shown to possess the ability to inhibit neurodegenerative processes in vitro. Nevertheless, in the Central Nervous Systems domain, there is little information on their impact on cell functions, especially on neuronal cells. In this work, we examined the influence of two VPD (VPD1 and VPD3) of zero generation (G0) on murine hippocampal cell line (named mHippoE-18). Extended analyses of cell responses to these nanomolecules comprised cytotoxicity test, reactive oxygen species (ROS) generation studies, mitochondrial membrane potential (ΔΨm) assay, cell death detection, cell morphology assessment, cell cycle studies, as well as measurements of catalase (CAT) activity and glutathione (GSH) level. The results indicate that VPD1 is more toxic than VPD3. However, these two tested dendrimers did not cause a strong cellular response, and induced a low level of apoptosis. Interestingly, VPD1 and VPD3 treatment led to a small decline in ROS level compared to untreated cells, which correlated with slightly increased catalase activity. This result indicates that the VPDs can indirectly lower the level of ROS in cells. Summarising, low-cytotoxicity on mHippoE-18 cells together with their ability to quench ROS, make the VPDs very promising nanodevices for future applications in the biomedical field as nanocarriers and/or drugs per se.

Analysis of biotinylated generation 4 poly(amidoamine) (PAMAM) dendrimer distribution in the rat brain and toxicity in a cellular model of the blood-brain barrier

Dendrimers are highly customizable nanopolymers with qualities that make them ideal for drug delivery. The high binding affinity of biotin/avidin provides a useful approach to fluorescently label synthesized dendrimer-conjugates in cells and tissues. In addition, biotin may facilitate delivery of dendrimers through the blood-brain barrier (BBB) via carrier-mediated endocytosis. The purpose of this research was to: (1) measure toxicity using lactate dehydrogenase (LDH) assays of generation (G)4 biotinylated and non-biotinylated poly(amidoamine) (PAMAM) dendrimers in a co-culture model of the BBB, (2) determine distribution of dendrimers in the rat brain, kidney, and liver following systemic administration of dendrimers, and (3) conduct atomic force microscopy (AFM) on rat brain sections following systemic administration of dendrimers. LDH measurements showed that biotinylated dendrimers were toxic to cell co-culture after 48 h of treatment. Distribution studies showed evidence of biotinylated and non-biotinylated PAMAM dendrimers in brain. AFM studies showed evidence of dendrimers only in brain tissue of treated rats. These results indicate that biotinylation does not decrease toxicity associated with PAMAM dendrimers and that biotinylated PAMAM dendrimers distribute in the brain. Furthermore, this article provides evidence of nanoparticles in brain tissue following systemic administration of nanoparticles supported by both fluorescence microscopy and AFM.

Multifunctional dendrimer-based nanoparticles for in vivo MR/CT dual-modal molecular imaging of breast cancer

Development of dual-mode or multi-mode imaging contrast agents is important for accurate and self-confirmatory diagnosis of cancer. We report a new multifunctional, dendrimer-based gold nanoparticle (AuNP) as a dual-modality contrast agent for magnetic resonance (MR)/computed tomography (CT) imaging of breast cancer cells in vitro and in vivo. In this study, amine-terminated generation 5 poly(amidoamine) dendrimers modified with gadolinium chelate (DOTA-NHS) and polyethylene glycol monomethyl ether were used as templates to synthesize AuNPs, followed by Gd(III) chelation and acetylation of the remaining dendrimer terminal amine groups; multifunctional dendrimer-entrapped AuNPs (Gd-Au DENPs) were formed. The formed Gd-Au DENPs were used for both in vitro and in vivo MR/CT imaging of human MCF-7 cancer cells. Both MR and CT images demonstrate that MCF-7 cells and the xenograft tumor model can be effectively imaged. The Gd-Au DENPs uptake, mainly in the cell cytoplasm, was confirmed by transmission electron microscopy. The cell cytotoxicity assay, cell morphology observation, and flow cytometry show that the developed Gd-Au DENPs have good biocompatibility in the given concentration range. Our results clearly suggest that the synthetic Gd-Au DENPs are amenable for dual-modality MR/CT imaging of breast cancer cells.

Reducing the cytotoxity of poly(amidoamine) dendrimers by modification of a single layer of carboxybetaine

The surface primary amines of generation five poly(amido amine) (G5 PAMAM) dendrimer were modified by different amounts of carboxybetaine acrylamide (CBAA). As a result, the fully modified molecules (CBAA-PAMAM-20, obtained from the 20:1 molar ratio of CBAA molecules to amino groups in modification solution) show excellent compatibility with protein and cells. CBAA-PAMAM-20 and fibrinogen (Fg) could coexist in solution without forming aggregation, indicating very weak interaction force between CBAA-PAMAM-20 and fibrinogen. CBAA-PAMAM-20 exhibits almost undetectable hemolytic activity, while other partially modified ones cause severe hemolysis and fibrinogen aggregation. Furthermore, the membrane of human umbilical vascular endothelial cell (HUVEC) remains intact after 24 h incubation with CBAA-PAMAM-20. The cytotoxicity assay of HUVEC cells and KB cells also showed that the CBAA-PAMAM-20 was not cytotoxic up to a 2 mg/mL concentration (>90% cell viability). In short, a thin compact layer of zwitterionic carboxybetaine could reduce the cytotoxicity of PAMAM through minimizing the interaction with protein and cell membranes, which suggest that the carboxybetaine-coated PAMAM could be a useful platform for biocompatible carriers to load contrast agents and drugs.

Generation of intracellular reactive oxygen species and genotoxicity effect to exposure of nanosized polyamidoamine (PAMAM) dendrimers in PLHC-1 cells in vitro

Polyamidoamine (PAMAM) dendrimers have previously been demonstrated to elicit systematically variable cyto- and eco-toxic responses, promising as the basis for structure-activity relationships governing nanotoxicological responses. In this study, increased production of intracellular reactive oxygen species (ROS), genotoxicity and apoptosis due to in vitro exposure of fish hepatocellular carcinoma cells to dendrimer generations G4, G5 and G6 is demonstrated. A PAMAM dendrimer generation dependent increase in ROS and genotoxicity was observed, consistent with our previous studies. The toxicological responses correlate well with the nanoparticle surface chemistry, specifically, the number of surface amino groups per generation. Although ROS production initially increases approximately linearly, it saturates at higher doses. Notably, normalized to the molar dose of surface amino groups, the dose-dependent ROS production for different generations overlap exactly, indicating that the response is due to these functional units. The genotoxicity response is also well correlated to the number of surface amino groups and therefore generation of PAMAM dendrimers. The observed genotoxicity, related to DNA damage, is related to the generation and dose dependent production of intracellular ROS, at low levels. At the higher ROS levels, increased DNA damage is associated with the onset of necrosis.

Genotoxicity of different nanocarriers: possible modifications for the delivery of nucleic acids

The prevention of cyto- and genotoxicity of nanocarriers is an important task in nanomedicine. In the present investigation, we, at the first time using similar experimental conditions, compared genotoxicity of nanocarriers with different composition, architecture, size, molecular weight and charge. Poly(ethylene glycol) polymers, neutral and cationic liposomes, micelles, poly(amindo amine) and poly(propyleneimine) dendrimers, quantum dots, mesoporous silica, and supermagnetic iron oxide (SPIO) nanoparticles were studied. All nanoparticles were used in non-cytotoxic concentrations. However, even in these concentrations, positively charged cationic liposomes, dendrimers, and SPIO nanoparticles induced genotoxicity leading to the significant formation of micronuclei in cells. Negatively charged and neutral nanocarriers were not genotoxic. A strong positive correlation was found between the number of formed micronuclei and the positive charge of nanocarriers. We proposed modifications of both types of dendrimers and SPIO nanoparticles that substantially decreased their genotoxicity and allowed for an efficient intracellular delivery of nucleic acids.

Functionalization of magnetic nanoparticles with dendritic-linear-brush-like triblock copolymers and their drug release properties

Novel water-soluble dendritic-linear-brush-like triblock copolymer polyamidoamine-b-poly(2-(dimethylamino)ethyl methacrylate)-b-poly(poly(ethylene glycol) methyl ether methacrylate) (PAMAM-b-PDMAEMA-b-PPEGMA)-grafted superparamagnetic iron oxide nanoparticles (SPIONs) were successfully prepared via a two-step copper-mediated atom transfer radical polymerization (ATRP) method. The macroinitiators were immobilized on the surface of Fe(3)O(4) nanoparticles via effective ligand exchange of oleic acid with the propargyl focal point PAMAM-typed dendron (generation 2.0, denoted as propargyl-D(2.0)) containing four carboxyl acid end groups, following a click reaction with 2'-azidoethyl-2-bromoisobutylate (AEBIB). PDMAEMA and PPEGMA were grown gradually from nanoparticle surfaces using the "grafting from" approach, which rendered the SPIONs soluble in water and reversed aggregation. To the best of our knowledge, this is the first report that describes the functionalization of magnetic nanoparticles with dendritic-linear-brush-like triblock copolymers. The modified nanoparticles were systematically studied via TEM, FT-IR, DLS, XRD, NMR, TGA, and magnetization measurements. DLS measurement confirmed that the obtained dendritic-linear-brush-like triblock copolymer-grafted SPIONs had a uniform hydrodynamic particle size of average diameter less than 30 nm. The dendritic-linear-brush-like triblock copolymer-grafted SPIONs possessed excellent biocompatibility by methyl tetrazolium (MTT) assays against NIH3T3 cells and hemolysis assays with rabbit erythrocytes. Furthermore, an anticancer drug, doxorubicin (Dox), was used as a model drug and loaded into the dendritic-linear-brush-like triblock copolymer-grafted SPIONs, and subsequently, the drug releases were performed in phosphoric acid buffer solution pH = 4.7, 7.4, or 11.0 at 37 °C. The results verify that the dendritic-linear-brush-like triblock copolymer-grafted SPIONs possess pH-responsive drug release behavior. The Dox dose of the loaded and free drug required for 50% cellular growth inhibition was 2.72 and 0.72 μm/mL, respectively, according to MTT assay against a Hella cell line in vitro. Therefore, on the basis of its biocompatibility and drug release effect, the modified SPION could provide a charming opportunity to design some excellent drug delivery systems for therapeutic applications.

Polyamidoamine dendrimer nanoparticle cytotoxicity, oxidative stress, caspase activation and inflammatory response: experimental observation and numerical simulation

Mechanisms underlying the in vitro cytotoxicity of Polyamidoamine nano-dendrimers in human keratinocytes are explored. Previous studies demonstrated a systematic, dendrimer-generation-dependent cytotoxicity, oxidative stress, and genotoxicity. The emerging picture is of dendrimer endocytosis, endosomal rupture and subsequent mitochondrial attack and cell death. To understand the underlying mechanisms, the evolution of reactive oxygen species, intracellular glutathione, caspase activation, mitochondrial membrane potential decay, and inflammatory responses have been examined. Early-stage responses are associated with endosomal encapsulation, later-stage with mitochondrial attack. In all cases, the magnitude and evolution of responses depend on dendrimer generation and dose. The early-stage response is modelled using a rate equation approach, qualitatively reproducing the time, dose and generation dependences, using only two variable parameters. The dependence of the response on the nanoparticle physicochemical properties can thus be separated from internal cellular parameters, and responses can be quantified in terms of rate constants rather than commonly employed effective concentrations.

FROM THE CLINICAL EDITOR

This contribution reports on the intracellular mechanism of PAMAM dendrimer cytotoxicity in human keratinocytes. In all cases, the magnitude and evolution of responses depend on dendrimer generation and dose. Experimental data were supported by numerical simulation using only two variables. It is suggested that responses can be quantified in terms of rate constants rather than effective concentrations.

Dendrimers for pharmaceutical and biomedical applications

Dendrimers are a unique class of synthetic macromolecules having a highly branched, three-dimensional, nanoscale architecture with very low polydispersity and high functionality. Structural advantages allow dendrimers to play an important role in the fields of nanotechnology, pharmaceutical and medicinal chemistry. This review discusses several aspects of dendrimers, including preparation, dendrimer-drug coupling chemistry, structural models of dendrimer-based drug delivery systems, and physicochemical and toxicological properties.

The inhibition of Th17 immune response in vitro and in vivo by the carbosilane dendrimer 2G-NN16

We evaluated the 2G-NN16-carbosilane dendrimer activities in Th17 response as a potential therapy for Th17 deregulated pathologies. IL17A, IL17F, IL22, IL23 and other interleukins secreted by Th17 cells CD4+ cells were down regulated when cells were cultured in the presence of this dendrimer. Furthermore, IL17F and IL17A protein levels in splenocytes from mice pretreated with 2G-NN16 dendrimer in a Th17 induction mouse model were lower than those corresponding to PBS treated mice. Treatment of mice with 2G-NN16 inhibited the Th17 response causing much more pathogenicity as indicated by the increase in the number of Candida albicans colonies in the kidneys as compared to PBS-treated mice. All these results suggest a potential pharmacological application for this dendrimer in the therapy of Th17-mediated diseases.

Cytotoxicity and genotoxicity of cationic phosphorus-containing dendrimers

Cationic phosphorus-containing dendrimers (CPDs) are a class of highly-branched polymers with potential medical relevance. However, little is known about CPD modes of interactions with cell and its components, including DNA. In the present work we investigated cytotoxicity and genotoxicity of CPDs generation 3 and 4 (CPD G3 and CPD G4) in human mononuclear blood cells, A549 human cancer cells and human gingival fibroblasts (HGFs). CPD G3 and CPD G4 at concentrations up to 10 μM induced a concentration-dependent decrease in cell viability as assessed by flow cytometry. Both compounds did not induce breaks in isolated DNA as evaluated by the plasmid relaxation assay but they induced DNA cross-links in the cells, as examined by comet assay. CPD G3 and 4 induced slight perturbations in the cell cycle leading to a decrease in the G2/M cell population accompanied by an increase in the S cell population. Upon treatment with CPDs, the cells showed changes in their morphology, including loss of cell attachment, disruption of cell membrane and nucleus condensation. Our results indicate that CPD G3 and G4 are cytotoxic and genotoxic for the assorted human cells. Therefore, CPDs may form stable complexes with DNA and interfere with cellular processes.

Stability, antimicrobial activity, and cytotoxicity of poly(amidoamine) dendrimers on titanium substrates

In this article, we present the first report on the antibacterial activity and cytotoxicity of poly(amidoamine) (PAMAM) dendrimers immobilized on three types of titanium-based substrates with and without calcium phosphate coating. We show that the amino-terminated PAMAM dendrimers modified with various percentages (0-60%) of poly(ethylene glycol) (PEG) strongly adsorbed on the titanium-based substrates. The resultant dendrimer films effectively inhibited the colonization of the Gram-negative bacteria Pseudomonas aeruginosa (strain PAO1) and, to a lesser extent, the Gram-positive bacteria Staphylococcus aureus (SA). The antibacterial activity of the films was maintained even after storage of the samples in PBS for up to 30 days. In addition, the dendrimer films had a low cytotoxicity to human bone mesenchymal stem cells (hMSCs) and did not alter the osteoblast gene expression promoted by the calcium phosphate coating.

Preparation of dexamethasone-based cationic liposome and its application to gene delivery in vitro

In this study, dexamethasone was conjugated to PAMAM dendrimer (generation 0) and its gene transfection efficiency was investigated. To make a liposomal solution for gene delivery, DOPE was used as a fusogenic helper lipid. In gel retardation assay, PAMAM-dexamethasone conjugate (PAM-Dex)/DOPE liposome/DNA complex was completely retarded at 8:1 N/P (nitrogen/phosphate) ratio. The physicochemical characteristics are studied by measuring the average size distribution and zeta-potential values of the complexes. In vitro transfection assay showed that the PAM-Dex/DOPE liposome/DNA complex displayed higher gene delivery efficiency compared to PAMAM/DNA complex. In addition, PAM-Dex/DOPE liposome showed the lowest toxicity compared to PAMAM, PEI 25 kD and Lipofectamine. These results indicate that PAM-Dex/DOPE liposome has a potential to be used as an efficient gene carrier for gene therapy.

Optimization and in vitro toxicity evaluation of G4 PAMAM dendrimer-risperidone complexes

Risperidone is an approved antipsychotic drug belonging to the chemical class of benzisoxazole. This drug has low solubility in aqueous medium and poor bioavailability due to extensive first-pass metabolism and high protein binding (>90%). As new strategies to improve treatments efficiency are needed, we have studied cationic G4 PAMAM dendrimers' performance to act as efficient nanocarriers for this therapeutic drug. In this respect, we explored dendrimer-risperidone complexation dependence on solvent, temperature, pH and salt concentration, as well as in vitro cytotoxicity measured on L929 cell line and human red blood cells. The best dendrimer-risperidone incorporation was achieved when a mixture of 70:30 and 90:10 v/v chloroform:methanol was used, obtaining 17 and 32 risperidone molecules per dendrimer, respectively. No cytotoxicity on L929 cells was found when dendrimer concentration was below 3 × 10(-2) μM and risperidone concentration below 5.1 μM. Also, no significant hemolysis or morphological changes were observed on human red blood cells. Finally, attempting to obtain an efficient drug delivery system for risperidone, incorporation in G4 PAMAM dendrimers was optimized, improving drug solubility with low cytotoxicity.

[Impact of polyamidoamine dendrimer liposome on the cellular uptake and cytotoxicity of colonic cancer cells]

OBJECTIVE

To evaluate the effects of polyamidoamine dendrimer (PAMAM) liposome as gene carriers on the cellular uptake and its cytotoxicity in colonic cancer cell.

METHODS

The liposome modified PAMAM was synthesized with liposome and polyamidoamine dendrimer. Plasmid PEGFP-N1 was mixed with the liposome-modified PAMAM or unmodified PAMAM to form nanoparticle complexes. The shape and size of the nanoparticle complexes were observed by transmission electron microscope and the zeta potential was measured by analytical tool. The encapsulating efficiency was determined by ultraviolet spectrophotometer in centrifuging method. After the cell lines SW620 (colonic cancer cell), MCF-7 (breast cancer cell), ECV304 (vascular endothelial cell) were transfected by the two kinds of PAMAM nanoparticle complexes, the flow cytometry was used to determine the uptake of enhanced green fluorescent protein (EGFP) gene. The cytotoxicity of PAMAM liposome nanoparticles and PAMAM nanoparticles was evaluated by MTT assay.

RESULTS

The diameter of liposome modified PAMAM complex was (192 ± 16) nm, and that of PAMAM complex was (189 ± 19) nm (P > 0.05); and the zeta potential of liposome modified PAMAM complex was higher than that of PAMAM complex [(42 ± 7) mV vs. (32 ± 7) mV, P < 0.05]. There was no significant difference in envelopment rate between the two groups [(82 ± 7)% vs. (84 ± 6)%, P > 0.05]. After the colonic cancer cell line SW620 was transfected with the two kinds of PAMAM nanoparticle complexes, the cellular uptake of the cells with the liposome-modified PAMAM complex was significantly higher than that of the cell with PAMAM complex (P < 0.05). The cellular survival rate of the cell lines with liposome-modified PAMAM complex was significantly higher than that of cell lines with PAMAM complex (P < 0.05).

CONCLUSION

The liposome modified PAMAM can improve gene transfection efficiency and suppress its cytotoxicity.

Development and characterization of triazine based dendrimers for delivery of antitumor agent

In the present study we developed the novel kind of triazine dendrimers by utilizing differential reactivity of the cyanuric chloride (triazine trichloride) which overcome the limitations associated with the others classes of dendrimers like toxicity, low yield, high synthesis cost etc. Triazine dendrimers were synthesized by divergent method using triazine trichloride as core and diethanolamine as branching unit to avoid the use of protecting group and functional group interconversion up to third generation. These hydroxyl terminated dendrimers were characterized by FTIR, 1HNMR, 13CNMR, ES mass spectroscopy, and by elemental analysis. The yield of pure G3 dendrimers was 63%. This novel dendrimers increases the aqueous solubility of hydrophobic drug Paclitaxel up to 0.562 mg/ml as well as showed control release behavior. Hemolytic and toxicology studies of this dendrimer in mice showed no adverse toxicity to the kidneys and the liver up to 200 mg/kg dose (i.p). Triazine being a hydrophobic compound, the core of this dendrimer is hydrophobic and supposed to easily incorporate the hydrophobic guest while presence of hydroxyl group on periphery increases its water solubility and reduces its toxicity; and thus it is useful in various fields like gene delivery, MRI contrasting agents, vaccines or as solubilization tool.